This invention relates to a reflex mirror for a single lens reflex (SLR) camera.
A conventional SLR camera has a reflex mirror which is raised up out of the photographic optical path when photographing an object, and which is lowered to direct light from the lens into a viewfinder/rangefinder (v/r) optical system for framing the object and focusing the camera. A variety of such reflex mirrors are well known in the art in which part of the mirror is semi-transparent, and light passing therethrough is utilized for light measurement in a built-in metering and control system.
Since the v/r optical system should appear as bright as possible during viewing, the peripheral areas of the mirror are totally reflective to thereby maximize the quantity of light delivered to the v/r optical system. The border lines between the totally reflective areas and the semi-transparent area and/or the semi-transparent area itself are typically formed by fine, closely spaced linear slits which form a shadow on the v/r optical system, thereby degrading the viewing conditions.
The v/r optical system usually also includes a distance measuring and focusing area (such as a micro-prism and a split image) comprising a plurality of prisms in a circular region whose center coincides with the optical axis, and the viewing brightness of this region is therefore very critical. The prior art reflex mirror arrangements, however, almost invariably attenuate the light in this critical circular region.